The parameter "MEANJZH", shown in panels (k-l) in Figure REF , stands for the mean current helicity with \(B_z\)  contribution.
Current helicity is crucial to magnetic energy build-up.
An explanation for the relationship between flares and current helicity is the
“\(\alpha -\) effect”, indicating that the energy of small-scale fluctuations of magnetic and
velocity fields could be transferred into the energy of large-scale currents [1]}.
The necessary condition for such effect may be the presence of the predominant sign of the
electric helicity over the whole AR.
[2]} conducted a statistical study involving 40 ARs and
suggested that the condition of the “\(\alpha -\) effect” worked in over \(90\%\)  of all the cases.
[3]} performed a simulation to study the current helicity.
They discussed the sources of the current helicity and suggested that field lines are skewed as
they cross the PIL.
Similar to current helicity, magnetic helicity is also believed to be closely related
to the mechanisms that drive solar activities.
“MEANALP”, shown in panels “o” to “p” in Figure REF , represents the mean characteristic twist parameter.
The method used to calculate this SHARP parameter was introduced by [4]} and adopted by [5]} in the SHARP package.
[6]} studied the 4 homologous events (all are eruptive flares) in AR 11283.
They analyzed the buildup process of the magnetic flux ropes (MFRs), especially the evolution of the magnetic helicity and the energy during the 4 eruptions.
Their results show that the MFRs, which are built up along the collisional polarity inversion lines (cPILs), store a large amount of energy and magnetic helicity.
The buildup process is involved with magnetic cancellation along the cPIL via collisional shearing, which may contribute to solar eruptions [7]}.
[8]} proposed several new parameters and investigated their ability in distinguishing eruptive and confined solar flares.
They found that the ratio between the “MEANALP” in the flaring PILs and the total unsigned flux in the whole AR (\(\alpha _{FPIL}/\Phi _{AR}\) ) is the most capable parameter to distinguish ARs that can produce eruptive flares.
In our work, as shown in Figure REF , the values of the parameters “MEANJZH” and “MEANALP” in the PIL area are about ten times the values in the whole AR, indicating that both current and magnetic helicities accumulate in the PIL area.
This is in agreement with the mentioned studies.
